Another year of interleague play is in the books, and as usual, the American League won the season series. The Junior Circuit has won each season since 2004, and there are several reasons for their dominance, some of which colleague Stan McNeal documented over the weekend.

Whatever the reasons are and whether you love or hate interleague play, it is wrapped up both for the year and as we’ve known it since its 1997 inception.

Here are some of the highs and lows from this season’s 252 interleague games:

The highlights

• Outside of King Felix, the Seattle Mariners aren’t known for their pitching prowess, or their hitting for that matter. And during interleague play it is worse than usual with a 4.47 ERA against National League teams.

But on June 8, the Mariners used six pitchers to no-hit the Los Angeles Dodgers for the fourth no-no of the season. Kevin Millwood started and five relievers—Charlie Furbush, Stephen Pryor, Lucas Luetge, Brandon League and Tom Wilhelmsen—secured a 1-0 victory.

• One of the most anticipated interleague series of the season happened two weekends ago, with the old guard, the New York Yankees, visiting the up-and-coming Washington Nationals.

Nothing went right for Washington as the Yankees swept the three games to put the young Nationals in their place. That set also came at the tail end of the Yankees’ 10-game winning streak that took them from third to first in the AL East.

• Not much has gone right for the Minnesota Twins this season, but Trevor Plouffe was an interleague beast. The 26-year-old is in his first full season in the majors, and he’s hit 14 homers, driven in 25 runs and has a 136 OPS-plus.

During interleague games, he has a .343 average (23-for-67), nine home runs, 15 RBIs, a .405 OBP, .806 slugging percentage and 1.211 OPS.

The lowlights

• Because the Colorado Rockies are one of the biggest messes in baseball right now, it stands to reason they are the worst interleague team in 2012. The Rockies went 2-13 against AL teams, and oddly their two wins came against the Detroit Tigers and Texas Rangers, two of the AL’s Super Six.

Since the second block of interleague games started June 8, the Rockies have moved Jeremy Guthrie to the bullpen, decided to try a crazy four-man rotation with a 75-pitch limit for the starters as a way to save the bullpen and their star, Troy Tulowitzki, is now out for up to two more months with a groin injury.

Basically, the Rockies are happy to see interleague play finish, and they probably aren’t too ecstatic about the rest of their season either.

• During that same Yankees-Nationals series, 19-year old Bryce Harper played the worst game of his life, going 0-for-7 with five strikeouts in a 14-inning loss.

In his first four at-bats, Harper saw 14 pitches and swung and missed at seven of them, not making contact until the 14th, when he flied out. His batting average went from .302 to .289 over those 14 innings.

Harper declined to speak to the media after the game, but the next day he told an assembled group, “I don’t think I’ve ever had a game like that in my life.”

• Just this past week, we had one of the more controversial and nonsensical events of the season happen. Tampa Bay reliever Joel Peralta was ejected from a game against the Nationals for having pine tar inside his glove.

That by itself isn’t a huge deal. He had it, he got caught, he was ejected and eventually suspended. That should have been the end of it, and it would have been had two veteran, white-haired managers not started acting like feuding teenagers.

First, Tampa Bay’s Joe Maddon used words such as “cowardly” and “bogus” and others not fit to print when talking about Washington’s calling out of Peralta, who used to be a National in 2010. Washington manager Davey Johnson shot back by telling Maddon to read the rulebook.

The next day, Maddon said he wouldn’t be surprised if free agents now stayed away from the Nationals, hinting that they aren’t a loyal club and will backstab a former player if it helps them win a game. Johnson came back with the sort of barb you might hear in a feud between teenagers, calling Maddon a “weird wuss,” whatever that means.